<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button class="red">web</button>
    <button >css</button>
    <script>
// let arr=[26,15,4,485];
//  arr=arr.filter((item)=>{
//     return item>100;
// });
// console.log(arr);

       let  btus=document.querySelectorAll("button");
       console.log(btus);
    //借用属性原型的filter,方系统的方法都是在原型里面！！
      btus=Array.prototype.filter.call(btus,(item)=>{
         return item.hasAttribute("class");
      });
      console.log(btus[0].innerHTML);//web   找到了web

    </script>
</body>
</html>